讲座-11

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3.正极和负极的选择最佳条件
The most advantageous combinations (最 有利的组合)of anode and cathode materials are those that will be give a high cell voltage and capacity （ 容 量 ). Such combinations may not always be practical, however, due to reactivity with other cell components, polarization(极化), difficulty in handling, high cost, and other deficiencies（不足 之处）. 25
The theoretical voltage is a function of the anode and cathode materials, the composition of the electrolyte and the temperature (usually stated at 25oC). The standard potential of a cell can be calculated from the standard electrode potentials as follows (the oxidation potential is the negative value of the reduction potential):
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3.额定容量（C额）
额定容量是指设计和制造电池时，规定或保证 电池在一定的放电条件下应该放出的最低限度 的电量。通常情况下，实际的容量比厂家保证 的容量高出5~15%。 化学电源的实际容量决定与活性物质的数量 及其利用率（）。由于内阻的存在，以及其 它各种原因，活性物质不可能完全被利用。活 性物质的利用率取决于电池的放电制度和电池 的结构。采用薄型电极和多孔电极，以减小电 池内阻，均可提高活性物质的利用率，从而提 高电池的实际输出容量。
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Free Energy- standard potential
Whenever a reaction occurs, there is a decrease in the free energy of the system, which is expressed as Go =Ho - TSo = -nFE0
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§1.4.3.电池的电压Voltage Level
1. The theoretical voltage. 2. The open-circuit voltage 3. The closed-circuit voltage 4. The nominal voltage (额定，标称电压） 5. The working voltage 6. The average voltage 7. The midpoint voltage 8. The end or cut-off voltage (截止电压）
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选择电解质的一般要求是：
The electrolyte must have good ionic conductivity but not be electronically conductive as this would cause internal shortcircuiting; Other important characteristics are nonreactivity with the electrode materials; little change in properties with change in temperature; safety in handling, and low cost.
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2.标称容量-The nominal capacity
标称容量是指在一定的放电条件电池实 际放出的电量。
电池的放电电流强度，温度和终止电压，称为 电池的放电制度。放电制度不同，容量不同。 恒电流放电：C = IT 恒电阻放电时：C = 0T IdT =1/R 0T VdT 近似计算公式为： C = 1/R V平T 式中I为放电电流，R为放电电阻，T为放电至终止 电压的时间，V平为电池的平均放电电压。
源自文库
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2.Charge
Negative electrode: cathodic reaction (reduction, gain of electrons)
Zn2+ + 2e→ Zn
Positive electrode: anodic reaction (oxidation, loss of electrons)
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4.比容量：
为了对不同的电池进行比较，常常引入比容 量这个概念。比容量是指单位重量或单位体积 的电池（或活性材料）所给出的容量，分别称 为重量比容量Ah/kg或体积比容量Ah/m3。 应当指出 ，一个电池的容量就是其中正极 （或负极）的容量，而不是正极容量与负极容 量之和，因为电池在工作时，通过正极和负极 的电量总是相等的。实际电池的容量决定与容 量较小的哪一个电极。
where F =constant known as Faraday (96,500 C or 26.8 Ah) n = number of electrons involved in stoichiometric reaction


E0 = standard potential, V
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1.Theoretical Voltage
2Cl- → Cl 2+ 2e
Overall reaction (charge):
Zn2+ + 2Cl- → Zn + Cl 2
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§1.4.2.电池的容量比容量
1.Theoretical Capacity (Coulombic)
The theoretical capacity of a cell is determined
§1.基本概念 BASIC CONCEPTS
§1.1化学电源的定义和必须具 备的条件 §1.2化学电源的组成 §1.3化学电源的分类 §1.4基本概念
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2.化学电源在实行能量转换的过程 中，必须具备两个必要的条件：
请问是那两个条件？ ①组成化学电源的两个电极上进行的氧 化还原过程，必须分别在两个分开的 区域进行，这一点区别于一般的氧化 还原反应； ②两电极的活性物质进行氧化还原反应 时所需电子必须由外电路传递，这一 点区别于金属腐蚀过程的微电极反应。 （为什么？） 17
Cl2 → 2Cl- - 2e Zn → Zn 2+ +2e
Zn +Cl2 → ZnCl2
1.36 V -(-0.76 V) 2.12V
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2. The open-circuit voltage is the voltage under a no-load condition and is usually a close approximation of the theoretical voltage. 3. The closed-circuit voltage is the voltage under a load condition. 4. The nominal voltage is one that is generally accepted as typical of the operating voltage of the battery as, for example, 1.5 V for a zinc-manganese dioxide battery.
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§1.3.1、按电解质种类分类
碱性电池:电解质为碱性溶液的电池。 酸性电池:电解质为酸性溶液的电 池。 中性电池:电解质为中性溶液的电池。 有机电解质电池:电解质为有机电解 质的电池。 固体电解质电池：聚合物，无机
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§1.3.2、按化学电源的工作性 质及贮存方式分类
Electrochemical cells and batteries are identified: 1.primary (nonrechargeable) 2.Secondary (rechargeable), depending on their capability of being electrically recharged 3. Reserve Batteries 4. Fuel Cell
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cathode (reduction potential) + Anode (oxidation potential) = standard cell potential.
For example, in the reaction Zn +Cl2 → ZnCl2, the standard cell potential is:
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§1.4基本概念
§1.4.1.充电电池的基本原理及电 池反应
§1.4.2.电池的容量和比容量 §1.4.3.电池的电压 §1.4.4.电池实际的能量和比能 §1.4.5.电池的功率与比功率
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1.4.1、充电电池的基本原理及 1. Discharge 电池反应
Negative electrode: anodic reaction (oxidation, loss of electrons) Zn → Zn2+ + 2e Positive electrode: cathodic reaction (reduction, gain of electrons) Cl 2+ 2e → 2ClOverall reaction (discharge): Zn + Cl 2→ Zn2+ + 2Cl-(ZnCl2 )
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5. The working voltage is more representative of the actual operating voltage of the battery under load and will be lower than the open-circuit voltage. 6. The average voltage is the voltage averaged during the discharge. 7. The midpoint voltage is the central voltage during the discharge of the cell or battery. 8. The end or cut-off voltage is designated(指定） as the end of the discharge. Usually it is the voltage above which most of the capacity of the cell or battery has been delivered.
§1.2.1电极——正极和负极 1.定义

The cathode or positive electrode — the oxidizing electrode—which accepts electrons from the external circuit and is reduced during the electrochemical reaction. The anode or negative electrode —the reducing or fuel electrode—which gives up electrons to the external circuit and is oxidized during the electrochemical reaction.
by the amount of active materials in the cell. Theoretically 1 gram-equivalent weight of material will deliver（释放） 96,487 C or 26.8 Ah. Hence, the theoretical capacity of the Zn/Cl2 cell is 0.394 Ah/g, that is, Zn + Cl2 → ZnCl2 (0.82 Ah/g) (0.76 Ah/g) 1.22 g/Ah +1.32 g/Ah = 2.54 g/Ah or 0.394 Ah/g